1. Field of the Invention
The present invention is generally concerned with clutches, usually called "wet" clutches, in which the friction disk or disks employed are immersed in an appropriate liquid, which in practice is oil.
It is more particularly directed to such clutches in which the oil is systematically circulated for simpler and above all faster evacuation of the heat energy produced on engaging or disengaging the clutch, especially when such actions follow on in quick succession and/or when it is a question not of a simple interruption clutch but of a starting clutch, that is to say a clutch through which all of the motor torque is passed, starting with the equipment served more or less completely stopped.
2. Description of the prior act
This is the case with mechanical transmission automobile vehicles, for example, and especially in the case of automobiles where the transmission comprises a variable speed drive in addition to the clutch.
A significant quantity of heat energy has to be removed on each start-up and if there are repetitive start-ups without this heat energy being appropriately dissipated the temperature may increase rapidly with the risk of the more fragile components being damaged and, in particular, of the friction facings concerned being burnt.
To minimize this risk it is known practise to use a plurality of friction disks alternating with intermediate disks.
The corresponding implementations necessarily have a non-negligible overall axial dimension, however, which makes it difficult to install them on automobiles, as the space available is in this case particularly restricted.
French Pat. No. 983.867 of Mar. 31, 1949 proposes a single-disk implementation, however. In this implementation a single friction disk is employed and there are provided within a casing, one of each side of the friction disk, two generally annular plates which are movable axially relative to each other for axially clamping the friction disk and one of which, hereinafter referred to for convenience as the pressure plate, is acted on by control means adapted to urge it towards the other, while this other plate, hereinafter referred to for convenience as the reaction plate, is adapted to support the assembly axially.
In this implementation, and in the conventional manner, the reaction plate is in practice a relatively massive part attached to the casing circumferentially and axially.
Although this makes it possible to provide oil circulation channels on the back of the pressure plate to promote coverage by the oil, it is not a simple matter to make the same provision for the reaction plate.
As a consequence of this, the two sides of the friction disk are cooled to different extents.
If other steps were not taken, this would result in gradual deterioration of the geometry of the friction disk and unequal wear of the corresponding friction facings.
In the implementation described in the aforementioned French patent the friction disk employed is not a conventional friction disk, that is a friction disk with friction facings at the periphery of a flange, but rather a special friction disk.
This friction disk reduces to a flange appropriately reinforced to oppose any distortion and the friction facings are carried one by the pressure plate and the other by the reaction plates, being appropriately and firmly attached thereto.
A general objective of the present invention is an arrangement making it possible to use a conventional friction disk in a circulating oil clutch and conferring further advantages.